I often see other anarchists emphasizing "exit" as the means for the customers to control the agencies. The analogy into our world of markets is good, but not great. You can see how, if the agency is somewhat nice to begin with, this would work. And in fact, if you're the sort of person that anarchy appeals to, you'll be immediately attracted to the idea of wielding that sort of power over your government. But... this still assumes the agency is nice enough to let you exit.
What if your agency is not nice? What if it turns rogue, and enslaves you? They've got the guns, right? What about company towns?
One answer to this is simple: in the real world you can't truly guarantee anything. If you set up an anarchy “wrong”, then abuse can happen. But this is not a problem unique to anarchy; states also have the seeds of tyranny in them. Even seemingly nice democracies, like Weimar Germany.
However, let us take some hope from the world of states. Consider all of the inventions men have invented to rein in the state. I would argue that none have been fully effective, but some have had real effect. I am thinking here of these:
- human rights
- civil rights - habeas corpus, trial by jury, etc.
- armed people/militia
- separation of powers
- church/state separation
OK, so here's my big idea: all of these state-limitation techniques could be applied to anarchic protection agencies. None of them rely on the state being a state per se; that is, none of them require a monopoly on legitimized violence. Rather, they could be applied by any “government”.
Put another way, the agencies in ancap are weaker than states. Any institution which serves to rein in the state, must also serve to limit ancap agencies, unless somehow it relies on the monopoly of coercion. Furthermore, in ancap you add a brake that is far, far more powerful than any of those above: exit. Exit alone won’t do the trick, I don’t think. But exit, along with all of the sorts of nice-state tricks we’ve invented so far, will.
In my opinion, ancap has not worked thus far for several reasons, not least of which is it is hard to get going. I analogize it to an arch: very stable once set up, but not likely to just happen. Rather it requires “scaffolding”, and states by their nature won’t allow the “scaffold” to be kicked away.
However, there may be another reason why ancap hasn’t taken over yet: it requires a certain level of technology. I think, at minimum, it requires technologies only invented during the Enlightenment - those listed above.